Vernon Schryver <v...@rhyolite.com> wrote: > > > [ANY query for combined MX/A lookup was] a bad hack then and it > > has remained a bad hack :-) > > I would not agree if you could rely on the open resolvers continuing > to do what they're doing, if you didn't care about parsing 3 or 4 > KBytes of irrelevant bits to get the RRsets you want, and if you don't > care about spending 9 or 10 IP packets on a truncated UDP responce and > then a full TCP response instead of 6 on 3 separate queries. > > With BIND as your DNS server, it could be a win for bursts of mail to > a single SMTP server if your SMTP client is too dumb to do the obvious, > safe caching. At worst you would need to ask for ANY, MX, A, and AAAA, > but some of the time the ANY would have all of the RRsets.
There are other caveats: The ANY query does not trigger additional section processing, so if you find MX records in the result you have to make follow-up queries to get the A and AAAA records of the targets; if you made an MX query in the first place you often don't need to make more queries. The ANY query does not trigger alias processing, so if there is a CNAME chain you have to follow it yourself. This is a waste because if you made an MX query in the first place the server would have given you the whole chain without further queries. Tony. -- f.anthony.n.finch <d...@dotat.at> http://dotat.at/ Forties, Cromarty: East, veering southeast, 4 or 5, occasionally 6 at first. Rough, becoming slight or moderate. Showers, rain at first. Moderate or good, occasionally poor at first. _______________________________________________ Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe from this list bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
